Primarily solid concentrate which contains a biocide

ABSTRACT

A microbiocide-containing concentrate for use in thermoplastic polymers as well as in plastisols, is disclosed. The concentrate is primarily solid at ambient conditions and comprises from 1-30 wt% of a microbiocide, a polymer plasticizer and up to 20 wt% of a thermoplastic resin. These concentrates are primarily useful as masterbatch compositions used for incorporation into polymers in order to protect said polymers from fungal or bacterial attack. Along these lines, the present document also discloses processes for incorporating these materials into a polymer or plastisol, and polymers or plastisols made by these processes.

BACKGROUND OF THE INVENTION

The present invention relates to a concentrate which contains a biocideand is primarily solid under ambient conditions. By primarily solid ismeant solid, wax-like or having another non-gas and non-liquidappearance, such as a gel or paste composition.

Polymer compositions are protected against fungal or bacterial attack bythe incorporation therein of a microbiocide to prevent deterioration ofthe polymer composition due to microbiological attack on the susceptibleportion of its components. For example, German Patent DE 1,288,790discloses the incorporation of urea or thiourea compounds, optionallytogether with a plasticizer, into polymers to impart antimicrobiocidalproperties to the polymers. Furthermore, U.S. Pat. No. 3,864,468discloses the incorporation of microbiocides, such as10,10'-oxybisphenoxyarsine (OBPA), into plastisols which may compriseliquid plasticizers, such as dioctylphthalate.

In order for the microbiocide to be effective in the polymercomposition, it is necessary that it be compatible therewith anduniformly dispersable therein to avoid the formation of areas within thepolymer which contain insufficient biocide to prevent polymerdeterioration.

To avoid toxicological problems related to the handling of the puremicrobiocide, microbiocides are presently added to polymer compositionsas a microbiocide-containing concentrate. Said concentrate can takedifferent forms, such as: a liquid, a powder, or a non-powdery solid.

Liquid concentrates are usually based on a plasticizer which is liquidat ambient conditions in combination with a cosolvent. By ambientconditions is meant: standard pressure and room temperature (about20°-30° C.). Without a cosolvent only low concentrations of themicrobiocide can be obtained due to the low solubility of commonly usedmicrobiocides in liquid plasticizers. Said cosolvent, however, maydestabilize the concentrate or adversely effect the polymer compositionwith which it is to be mixed. A further problem arises from the factthat it is difficult to completely remove a liquid concentrate frompackaging used for transport or storage, so that unless it can be reusedor cleaned, this packaging becomes toxic waste.

Problems related to the toxicity of such compositions can be overcome byincorporating the microbiocide in a solid composition in such a way thatit is immobilised under conditions that allow transport, storage, andthe like. The following two ways of doing this were developed in thepast.

U.S. Pat. No. 4,086,297 describes a method of making a concentrate to beincorporated into a second, polymeric composition, which concentratecomprises a homogeneous, melt-blended mixture of a biocide and at least24 wt. % of a solid thermoplastic resin. This concentrate, however,cannot be added successfully to a plastisol because of its relativelyhigh melting point and low solubility therein.

U.S. Pat. No. 4,663,359 describes a method of making a powderyconcentrate in which a microbiocide is absorbed on a porous resinpowder. Said concentrate is said to be mixable with a plastisol,however, it has been found that such dry blends are not universallycompatible with pastisols. In other words, it is necessary to preparevarious different types of dry blends in order to obtain the desiredcompatibility with plastisols. A plastisol can, therefor, only beadequately protected against fungal or bacterial attack if more of theconcentrate is added than would be needed in case of a homogeneousdistribution, thereby increasing the toxicity of the plastisol.Accordingly, a need exits for a microbiocide concentrate which can beused to make a homogeneous distribution of a microbiocide in aplastisol.

Further, the powdery concentrate is also susceptible to the formation offines which may lead to a dust hazard. Thus, there is also a need for asolid masterbatch formulation which is not susceptible to the formationof fines. These and other objects of the invention will be apparent toone of oridinary skill in the art from the summary and detaileddescription which follow.

SUMMARY OF THE INVENTION

The present invention provides a primarily solid concentrate comprisinga microbiocide which can be homogeneously distributed in a plastisol,and does not have the disadvantages of the prior art products previouslymentioned. Other applications, such as the protection of non-plastisolplastics, are also possible. If the concentrates according to theinvention are to be melt-blended with polymers, care should be taken notto use concentrates which will degrade at the melting temperature of thepolymer.

The invention is characterized by the fact that the concentratecomprises:

1-30 wt. % of a microbiocide selected from the group consisting ofphenoxyarsene compounds, copper compounds, and zinc compounds havingmicrobiocidal activity,

at least one plasticizer which is solid under ambient conditions in asufficient amount to act as a carrier for the microbiocide, and

0-20 wt%, of a thermoplastic resin. Other aspects of the inventioninclude a process for incorporating microbiocide in a polymer, as wellas, in a plastisol.

DETAILED DESCRIPTION OF THE INVENTION

A concentrate according to the present invention can be prepared byheating a plasticizer which is solid under ambient conditions, to atemperature at or above its reel ting point and mixing a microbiocidematerial in the melted plasticizer until a homogeneous mixture isobtained. The homogeneous mixture is then rapidly cooled to roomtemperature to produce a solid, microbiocide-containing concentrate.This concentrate is preferably particulated in order to render it easierto handle. Particulation can be done for example, by pelletization,flaking or granulation.

At any stage during the process of making the concentrate, typicaladditives used in polymer masterbatches may be incorporated into theconcentrate. For example, coloring agents, surface active agents,diluents, anti-dusting agents and small amounts of polymer may all beemployed as additives to the concentrate. Said additives should becompatible with the plasticizer, the microbiocide, and the polymer orthe plastisol to which the concentrate will later be added. Theseadditives may influence the melting point of the concentrate and thuscare should be taken to avoid lowering the melting point of theconcentrate to below ambient temperature by incorporation of additive(s)therein.

The solid plasticizers which can be used must be compatible with thepolymer composition with which they are to be mixed. This can be easilyaccomplished by the selection of known solid plasticizers for thepolymer which is to be protected from microbiocidal attack. Suchplasticizers should also exhibit a low toxicity to avoid producingconcentrates having an unacceptably high toxicity. Useful plasticizersinclude materials which are solid under ambient conditions and which areknown to be polymer plasticizers. For example glycols, C₁₆ -C₂₂ fattyalcohols, C₈ -C₂₂ fatty acids, phthalates and phosphates may be used.More preferred plasticizers are those which melt between about 40° C.and 110° C. such as, for example, triphenyl phosphate (TPP),dicyclohexyl phthalate (DC, HP), stearic acid, 1-hexadecanol,1-octadecanol, 1-tetradecanol, chlorinated paraffinic hydrocarbons andpolyethylene glycols. The advantages of selecting plasticizers whichmelt in this range are that only very small amounts of the microbiocideare vaporized at such low temperatures and thus the risk to workersmaking the concentrate is reduced when compared with the preparation ofsolid masterbatches from PVC wherein the microbiocide must be heated tomuch higher temperatures, and that the resultant concentrates can beremelted at relatively low temperatures. Of course, mixtures of solidplasticizers are also within the scope of the present invention.

A sufficient amount of the plasticizer must be employed to act as acarrier material for the microbiocide. The exact amount of plasticizerneeded will depend upon the type and concentration of the microbiocideas well as the types and amounts of other additives which may be presentin the concentrate. Usually, in excess of the minimum amount ofplasticizer will be employed in the concentrate in order to ensure thatthe toxicity level remains low. Thus, with the most preferred solidplasticizers, namely TPP and DCHP it is possible to make concentrateswith 40% of a microbiocide, based on the plasticizer. However, such highconcentrations of microbiocide are undesirable since the concentratewill be somewhat toxic. Accordingly, it is preferred to makeconcentrates containing 1-30 wt. % microbiocide, and more preferablyfrom 4-10 wt. % microbiocide, based on the concentrate. Theseconcentration ranges are generally higher than those obtainable byemploying liquid plasticizers wherein concentrations of 1-4 wt. % aregenerally employed. Thus, the present invention provides the ability toemploy a smaller volume of masterbatch which contains a largerconcentration of the microbiocide than could be safely incorporated incommercially available liquid masterbatches.

The microbiocide is a biocide which is also a solid under ambientconditions. The microbiocides to be used in the present invention arephenoxarsene compounds like 10,10'-oxybisphenoxarsine (OPBA), coppercompounds such as copper VIII hydroxy choline and various zincdithiocarbamates. OBPA, and materials like it, are preferred becausethey are solid and they provide sufficient microbiocidal activity evenat low concentration levels.

In some cases it may be desirable to add a small amount ofthermoplastic, resin to the concentrate. Generally, this resin will beadded to the melted plasticizer in powder form at a temperature highenough to ensure the dissolution of the resin in the concentrate. Thisthermoplastic resin is an optional component in the concentrate and maybe added in amounts of from 1 up to 20 wt. %, based on the concentrate.If larger amounts of the resin are employed, the resulting concentratewill suffer from the disadvantage that it will no longer be useful inplastisols due to its high reel ting point and lowered solubility in theplastisol.

The concentrate of the present invention is useful as a polymermasterbatch for protecting polymers from fungal or bacterial attack.Standard masterbatching methods can be employed to incorporate thepresent concentrates into polymers. Further, the present composition isparticularly advantageous since it may also be applied in plastisolapplications.

To use the present masterbatches in plastisols, the concentrate isdissolved in the plastisol under mild heating. The preferredplasticizers, TPP and DCHP are quite good in plastisol applicationssince concentrates made with these plasticizers can be dissolved quicklyand exhibit excellent compatibility in standard plastisols such as thosebased on dioctylphthalate (DOP). Once the concentrate is dissolved inthe plastisol, standard plastisol application techniques can be employedto provide coatings which are protected against bacterial and fungalattack.

The following examples are presented to further illustrate the presentinvention and are not to be construed as limiting the scope of theinvention in any way.

EXAMPLES 1-8

These examples illustrate how concentrates according to the inventionare made. Each of the formulations set forth below in Table I wasprepared by:

(i) heating the plasticizer to a temperature somewhat above its meltingpoint,

(ii) mixing the microbiocide in the melted plasticizer with stirringuntil it is dissolved,

(iii) if additives are used, mixing the additives in the mixture, and

(iv) cooling the resulting concentrate down to below its melting pointin order to let it solidify.

                                      TABLE I                                     __________________________________________________________________________    Concentrate No.                                                               (wt. %)   1   2   3   4   5   6   7   8                                       __________________________________________________________________________    OBPA       5.0                                                                               5.0                                                                               5.0                                                                               5.0                                                                               5.0                                                                               5.0                                                                               5.0                                                                               5.0                                    TPP       95.0                                                                              85.0                                                                              85.0                                                                              85.0                                                                              47.5                                                                              --  --                                          DCHP      --  --  --  --  --  85.0                                                                              75.0                                                                              47.5                                    stearic acid                                                                            --  10.0                                                                              --  --  --  --  --                                          glyceroltristearate                                                                     --  --  10.0                                                                              --  --  --  --                                          epoxidised palm oil                                                                     --  --  --  10.0                                                                              --  --  --                                          hexadecanol                                                                             --  --  --  --  47.5                                                                              10.0                                                                              --                                          paraffin  --  --  --  --  --  --  20.0                                        octadecanol                           47.5                                    melting point (°C.)                                                              48-51                                                                             42-44                                                                             48-50                                                                             47-49                                                                             42-46                                                                             42-60                                                                             46-62                                                                             50-52                                   __________________________________________________________________________

EXAMPLES 9-26

A number of solid masterbatch formulations were prepared based on 5 wt.% of microbiocide and 95 wt. % of plasticizer. These formulations arelisted in Table II.

These formulations were prepared by dissolving the microbiocide at about120° C. in the plasticizer followed by crystallization of themasterbatch according to the procedure of Examples 1-8. All of theseformulations exhibited good crystallization behavior indicating auniform distribution of microbiocide in the solid plasticizer as well assufficient solubility of the microbiocide in the plasticizer to prepare5 wt. % solutions.

                                      TABLE II                                    __________________________________________________________________________    Exper.                                                                            Fungicide   Carrier          Melting                                      No. (%)   Type  (%) Type         range (C.)                                   __________________________________________________________________________     9  5.0   OBPA  95.0                                                                              1-Hexadecanol                                                                              48-50                                        10  5.0   Copper (8)                                                                          95.0                                                                              1-Octadecanol                                                                              56-58                                        11  5.0   CPA   95.0                                                                              1-Octadecanol                                                                              56-58                                        12  5.0   OBPA  95.0                                                                              1-Octadecanol                                                                              56-58                                        13  5.0   ZDMC  95.0                                                                              1-Octadecanol                                                                              56-58                                        14  5.0   OBPA  95.0                                                                              1-Tetradecanol                                                                             37-38                                        15  5.0   OBPA  95.0                                                                              Cereclor S-70                                                                              58-70                                        16  5.0   Copper (8)                                                                          95.0                                                                              Polyethylene glycol 4000                                                                   54-58                                        17  5.0   CPA   95.0                                                                              Polyethylene glycol 4000                                                                   54-58                                        18  5.0   OBPA  95.0                                                                              Polyethylene glycol 4000                                                                   54-58                                        19  5.0   Copper (8)                                                                          95.0                                                                              Stearic Acid 67-69                                        20  5.0   CPA   95.0                                                                              Stearic Acid 67-69                                        21  5.0   OBPA  95.0                                                                              Stearic Acid 67-69                                        22  5.0   Copper (8)                                                                          95.0                                                                              Triphenylphosphate                                                                         48-51                                        23  5.0   CPA   95.0                                                                              Triphenylphosphate                                                                         48-51                                        24  5.0   OBPA  95.0                                                                              Triphenylphosphate                                                                         48-51                                        25  5.0   ZDBC  95.0                                                                              Triphenylphosphate                                                                         48-51                                        26  5.0   ZDMC  95.0                                                                              Triphenylphosphate                                                                         48-51                                        __________________________________________________________________________     Copper (8) = Copper (8) hydroxy chinoline                                     CPA = 10chlorophenoxarsine                                                    OBPA = 10,10'-oxy bis phenoxarsine                                            ZDBC = zinc dibutyl dithiocarbamate                                           ZDMC = zinc dimethyl dithiocarbamate                                          Cereclor S70 = chlorinated paraffinic hydrocarbons (ex. ICI)             

We claim:
 1. A concentrate which contains a biocide and is primarilysolid under ambient conditions, which comprises1-30 wt. % of amicrobiocide selected from the group consisting of phenoxyarsenecompounds, copper compounds and zinc compounds, having microbiocidalactivity, a plasticizer which is solid under ambient conditions, in asufficient amount to act as a carrier for the microbiocide, and 0-20 wt.% of a thermoplastic resin.
 2. The concentrate according to claim 1,wherein the phenoxyarsene compound is 10,10'-oxybisphenoxyarsine.
 3. Theconcentrate according to claim 1, wherein the plasticizer is selectedfrom the group consisting of C₈ -C₂₂ fatty acids, C₁₆ -C₂₂ aliphaticalcohols, polyethylene glycols, phthalates and phosphates.
 4. Theconcentrate according to claim 3, wherein the plasticizer is selectedfrom the group consisting of triphenylphosphate, dicyclohexylphthalate,1-hexadecanol, 1-octadecanol, 1-tetradecanot, chlorinated paraffinichydrocarbons, polyethylene glycol and stearic acid.
 5. The concentrateaccording to claim 1, which comprises from 1-20 wt% of a thermoplasticresin.
 6. A process of incorporating a microbiocide in a polymer,wherein the concentrate according to claim 1 is incorporated in apolymer.
 7. A process of incorporating a microbiocide in a plastisol,wherein the concentrate according to claim 1 is incorporated in aplastisol.